Myocarditis occurs commonly in AIDS. The etiology and pathogenesis of the lesion is obscure, and its relevance to survival unknown. Disseminated cytomegalovirus (CMV) infections almost invariably occur in AIDS patient. And, CMV causes myocarditis in both immunosuppressed and immunologically intact humans. CMV infected adult mice develop myocarditis characterized by interstitial cellular infiltration in the heart. When animals are administered monoclonal anti-CD4+ T lymphocytes antibody, the infection is severe and prominent myocardial lesions develop. In contrast, elimination of CD8+ T cells with monoclonal antibody does not result in myocarditis and the infectious process is not accentuated. It remains to be determined why and how CD4- animals develop myocarditis. It could be due to viral damage to the heart, or an immunopathological process, or a combination of the two processes. The proposed studies will explore this model disease and its applicability to understanding AIDS-associated myocarditis. Our laboratory has an extensive experience with viral induced, immunopathologically mediated coxsackievirus B myocarditis. The approaches developed in our previous work will be applied to the CMV problem.